Human cytomegaloviruses (CMV) are ubiquitous in the human population. Acquired infections with this virus occur in normal hosts as well as premature infants, the immunocompromised, and transplant recipients. In spite of extensive literature and knowledge about the protean clinical manifestations, pathobiology, and seroepidemiology of CMV infections there is a great deal unknown about the transmission and epidemiology of CMV infections. This is due to the ubiquitous nature of this virus, the high frequency of inapparent infections and the lack of multiple serotypes for epidemiological studies. As a means of providing the necessary laboratory markers required to supplement epidemiological studies, the usefulness of restriction enzyme analysis of CMV DNA as a rapid and simple method of strain identification will be determined. The feasibility of using a modifed ELISA for detection of CMV in epidemiological studies will be confirmed. The incidence and prevalence of acquired CMV infections in a large intensive care nursery will be established. DNA endonuclease cleavage, combined with modified ELISA assay for rapid detection of CMV, will then be used to do epidemiological and transmission studies to answer the following questions: 1) Are differences in virulence or disease associated with different genetic strains of CMV? 2) With what frequency is CMV acquired from the maternal vaginal tract or cervix during birth? 3) Can household members transmit CMV to infants? 4) Are hospital personnel, blood, transfusions, or maternal colonization responsible for acquired CMV infection? 5) With what frequency do transplant recipients acquire CMV from donor organs or transfused blood? The answers to these questions are essential if CMV infections are to be prevented either by containment or the development of vaccines.